This invention relates to a video tape recorder (VTR) and, more particularly, to a tape address synchronizing apparatus for a VTR which synchronizes a tape address of the VTR to a predetermined address at a certain point.
When a video program recorded on a magnetic tape which is mounted on a playing VTR is to be edited into another magnetic tape located on a recording VTR, both VTRs rewind backward their respective magnetic tapes by a predetermined time (pre-roll time) from the edit point, and then, both VTRs turn on in the normal (forward) direction. In this manner, the two magnetic tapes are synchronized and the editing is begun at a desired point on the tape. During the pre-edit role, the speeds of one or both VTRs are controlled to align or synchronize the respective tapes. Accordingly, the tape addresses of both VTRs must be synchronized with each other during the pre-roll time. Such a tape address adjusting or synchronizing technique is disclosed in the U.S. patent application entitled "Tape Address Synchronizing Apparatus for Video Tape Recorder" which corresponds to Japanese Patent Application No. 58-90175 filed on May 23, 1983.
Recently, such synchronizing VTRs have also been used for producing special images such as still images, slow motion images and quick motion images. In an editing operation, however, where it is necessary to edit a program which includes a special image, a problem arises because the playing VTR is operated at a special speed corresponding to the special images (i.e., the playing VTR is operated at a slow speed while the recording VTR is operated at the normal speed so as to record a slow motion image). In this case, the pre-roll time provided to the playing VTR is different from that provided to the recording VTR. For example, when the playing VTR runs at 1/7 times normal speed to deliver the slow motion image, and the pre-roll time for the recording VTR is seven seconds, the pre-roll time of the playing VTR would be only one second. Furthermore, the updating rate of the tape address in the playing VTR is 1/7 the updating rate of the tape address in the recording VTR. Since a conventional tape address synchronizing apparatus is usable only when both the playing VTR and the recording VTR are operated at their normal speeds, the conventional tape address synchronization apparatus cannot be used to synchronize the tape address to a predetermined address with the required accuracy. By using the conventional apparatus, frame error of the tape address is generated by the tape address synchronizing apparatus. Therefore, with the apparatus of the prior art, accurate editing is not possible when the playing VTR is operated at a different speed, especially at a slow speed, such as when the slow motion images are recorded.